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For further information, see CMDT Part 39-16: Carcinoma of the Anus

Key Features

  • Carcinoma of the anus is relatively rare: only 2% of all gastrointestinal malignancies

  • Occurred in ~8590 patients in the United States in 2020

  • More commonly seen in women than in men (2:1 ratio)

  • Squamous cell carcinomas (SCC) make up the majority of anal cancers; adenocarcinomas account for the remainder

  • > 90% of anal cancers are associated with human papillomavirus (HPV) infection (most commonly, HPV-16 and HPV-18)

  • Increased incidence among

    • Women with HPV-associated cervical, vulvar, or vaginal squamous intraepithelial lesions or cancer

    • Men who have sex with men

    • Women and men who are HIV-positive or have received a solid organ transplant

Clinical Findings

  • Anal bleeding

  • Pain

  • Local mass

  • The lesion is often confused with hemorrhoids or other common anal disorders

  • Tumors tend to become annular, invade the sphincter, and spread upward via the lymphatics into the perirectal mesenteric lymphatic nodes


  • CT or MRI scans of the abdomen and pelvis are required to identify regional lymphadenopathy or metastatic disease at diagnosis

  • PET imaging may be used in conjunction


  • Wide local excision for small (< 2 cm) superficial lesions of the perianal skin

  • Combined-modality therapy for SCC of the anal canal as well as large perianal tumors invading the sphincter or rectum: external radiation plus simultaneous chemotherapy (5-fluorouracil plus mitomycin)

  • Local control achieved in approximately 80% of patients

  • Radical surgery (abdominoperineal resection) for patients in whom chemotherapy and radiation therapy fail

  • Metastatic disease is generally treated with carboplatin and paclitaxel

  • Checkpoint inhibitor therapy with either nivolumab or pembrolizumab has been shown in small studies to result in disease control in up to 46% of patients with chemotherapy-refractory, metastatic, or unresectable disease

  • Treatment of anal adenocarcinoma is like that of rectal adenocarcinoma with trimodality therapy: chemoradiotherapy, chemotherapy, and abdominoperineal resection

  • Surveillance includes

    • Digital rectal exam

    • Anoscopy

    • Inguinal lymph node palpation every 3–6 months for 5 years

    • CT scans of the chest, abdomen, and pelvis annually for 3 years

  • 5-year survival rate

    • 81% for localized tumors

    • ~ 30% for metastatic disease

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